Midget inductance tuning mechanism



y 1951 w. A. SCHAPER 2,555,248

umcmmmaucnucz TUNING uficamx'su Filed Aug. 12, 1946 //v VENTQE. Wu. m/ /H. fic'HA PER ATTORNEY.

Patented May 29, 1951 MIDGET INDUCTANCE TUNING MECHANISM William A. Schaper, Cicero, Ill., assignor to Aladdin Industries, Incorporated, a corporation of Illinois Application August 12, 1946, Serial No. 689,903

'7 Claims.

The invention pertains to mechanism for radio purposes by which permeability tuning may be effected in a plurality of radio circuits by the movement of a single tuning knob, and the invention is characterized by such a construction of the mechanism that the over-all dimensions of the tuning unit are reduced to a minimum. This result is secured by providing the unit with a narrow mounting strip of metal on which a strip of insulating material is secured, said structure having extending upwardly from its mid-portion an insulating post supporting one end of each of two coil forms, so that the coil forms are parallel with eachother and with the insulating strip, the support of said coil forms being such that one of said coil forms extends in one direction from said post and the other of said coil forms extends in the opposite direction therefrom. One end portion of the mounting plate supports a combined tuning knob and drum for rotary movement in such a manner that the knob is substantially parallel with said post. The opposite end of the mounting plate supports guiding mechanism for an endless flexible band, which guiding mechanism is substantially parallel with said post, and an endless flexible band extends around said guiding mechanism and also around the drum and is secured to said drum with the band under suitable tension, the side members of the said band extending preferably parallel with the coil forms supported by said post. The coil forms are preferably supported solely by said post, so that their other ends are free from support, and a ferromagnetic core is provided in each coil form for movement from and into the coil form at its supported end. Each of the cores is provided with a slender operating member in the form of a [metallic rod secured to the core and extending axially therefrom a short distance at which point the connecting rod is bent to extend towards one of the side members of the flexible band to which it is permanently attached, for example, by bending the end of the connecting rod against opposite sides of that part of said band, the pressure of the connection being preferably at a right angle to the direction of movement of said band. The connection of the core-connecting rods to the side members of the flexible band is made preferably in such a wa that for one position of the flexible band, both of the cores are entirely inserted in their coil forms, and for the other extreme position of the said band, both of the cores are in their outermost positions relatively to the coil forms.

The guiding mechanism for the flexible band preferably comprises two guiding rollers supported by slender studs of spring wire, which preferably comprise the end portions of a U-shaped spring wire member extending under the mounting plate and engaged by a tongue of said plate to hold the spring studs and guiding rollers in operative position on the other side of the plate.

The post construction supporting the coil forms, preferably comprises a U -shaped member of sheet insulating material, parts of the end portions of which preferably extend through and are secured to said insulating strip, and the insulating strip, said post and said coil forms are held in the positions described, by a tongue member formed preferably from the material of the mounting plate and extending upwardly therefrom through the insulating strip and through the post between the coil forms supported thereby, the parts being preferably held in that relation by suitable cement.

The tuning knob is preferably hollow and made of plastic material and Where the material is transparent, a graduated scale on paper or the like may be inserted in the hollow portion of the knob for cooperation With a fixed pointer adjacent said knob and supported by said mounting plate. The drum portion of the tuning knob is preferably provided with a slot or similar construction to engage the flexible member to prevent its slipping relatively to the drum.

The mounting plate is provided below the coil forms with cutout portions forming clearance openings around terminal lugs secured to or supported by the insulating strip, which lugs are connected with the windings carried by the coil forms.

It is found that cores of small diameter may be effectively employed for many purposes with a tuning mechanism of the kind described, and where the cores are, for example, in diameter, the over-all dimensions of the entire tuning unit, disregarding the extension of the terminal lug ends, may be substantially 3 long by high, by wide. This particularly adapts the tuning unit described, for use in midget radio receivers of the kind employed to selectively tune the stations of the broadcast band, although the tuning unit is not limited to that size or to such purposes.

The inventon will be best understood by reference to the accompanying drawings showing a preferred form thereof, in which:

Fig. 1 shows the tuning unit in plan view, to an enlarged scale,

Fig. 2 is a side elevation of the structure shown in Fig. 1,

Fig.3 is a bottom view of the tuning unit,

Figs. 4 and 5 are vertical sectional views of the structure shown in Fig. 2 taken along the lines 44 and 5-5 respectively in Fig. -2,

Fig. 6 is a bottom view of the tuning knob and drum removed from the rest of the structure, and

Fig. 7 is a sectional view of the knob and drum shown in Fig. 6 taken along the line 'l! in Fig. 6.

terial and having portions of its ends extending through the strip 2 and secured thereto as illustrated in Fig. 4, the parts being preferably secured together by suitable cement. The post 3 has extending therethrough one end of each of the coil forms 4 and 5 so that the said coil forms are parallel with each other and with the strip 2 and mounting plate I. The other ends of the coil forms 4 and 5 are preferably not supported in any way. The coil forms 4 and 5 contain ferromagnetic cores 6 and I which are movable axially in the coil forms for tuning purposes, said cores being movable into and from the ends of the coil forms supported by the post 3. One end of the mounting plate I supports a combined tuning knob and drum 8 on a stud 3 secured to the mounting plate so that the knob may be turned for tuning purposes. The other end of the mounting plate supports guiding rollers If} and II on spring studs l2 and I3 respectively, which studs are preferably of spring wire and comprise portions of a U-shaped member I4 the mid-portion of which passes around a tongue I5 formed from the mounting plate I. The spring member I4 is constructed so that when a desired tensional stress is exerted by the rollers I and II on an endless band It passing around said rollers, the latter are in substantial vertical position. The side portions of the spring member I4 extend from below the mounting plate I through notches in the end of said plate (Fig. 3), to form the spring studs I2 and I3, which notches prevent displacement of said studs relatively to said mounting plate.

The flexible band I6 may be of any suitable material, for example cord or flexible wire, and besides extending around the guide rollers I11 and II, it also passes around the drum portion I? of the tuning knob 8, to which drum portion it is secured to avoid slippage of the drum relatively to said band. Guide slots I8 (Figs. 4 and are provided in the post 3 for the band I6.

The cores 6 and I have extending from their outer ends, slender operating rods I9 and 20, which rods a short distance from said cores, are bent to extend towards the flexible band I6 around which the ends of said rods are tightly pressed so that movement of said band will be accurately communicated to said cores. Adjacent the drum II, the mounting plate I has formed therefrom an upwardly extending guiding member 2I to guide the flexible band I6 to proper position on the drum I1, and the drum is provided with a slot 22 (Fig. 6) through which the band extends to prevent slippage of the drum in the band. The member 2I passes through a slot in the adjacent end of the strip 2 and holds said end in place on the mounting plate I. To limit rotation of the knob 3, the drum I1 is provided with a projecting lug 23 for engaging stop lugs 24 and 25 (Fig. 3) extending upwardly from the mounting plate I. The side members of the band I5 are preferably located substantially in vertical planes respectively through the aXes of the coil forms '4 and 5, to afford support for the outer ends of the cores 6 and I in their outer positions.

The knob 8 preferably carries a graduated scale for co-operation with a pointer 26 extending from the mounting plate I. Said graduated scale may be made on the outer surface of the knob 8 or where said knob is of transparent material and hollow, as is preferably the case, said graduated scale may be on thin material such as paper or the like and placed inside of the knob, the purpose being to afford an indication of the tuned condition of the tuning unit at any time.

As shown in Fig. 3, the mounting plate I is cut away to provide clearance openings 21 and 28 around terminal lugs 29 and 30 carried by the insulating strip 2, to which lugs the windings 3| and 32 on the coil forms 4 and 5 are connected. The end one of the lugs 29 may be pressed against and soldered to the mounting plate I, and holds the adjacent end portion of the strip 2 in place on said mounting plate.

In making the clearance opening 28 in the mounting plate I, a narrow supporting and reinforcing tongue 33 is conveniently made from the mounting plate, which extends upwardly therefrom through the insulating strip 2 and between the coil forms 4 and 5 and through the top portion of the post 3 to stiffen and stabilize the post structure, said stiffening tongue being preferably secured to the post by suitable cement.

The construction described is adapted to produce a remarkably compact tuning unit, particularly where small cores 6 and I, for example in diameter, are employed, which cores are found to be satisfactory for many purposes. In such cases, it is found that the over-all length of the tuning unit may be about 3%,, the other dimensions being in the proportions shown in the drawings which, as stated, are all to an enlarged scale, which is the same for all of said figures of drawings.

While I have shown my invention in the particular embodiment above described, it will be understood that I do not limit myself thereto as I may employ equivalents thereof without departing from the scope of the appended claims.

Having thus described my invention, what I claim is:

1. Apparatus for supporting and operating permeability tuning radio mechanism of the movable core type, including in combination a nar-- row mounting plate, a post supported by and extending upwardly from the mid-portion of said mounting plate, a tuner comprising fixed me1nbers supported by said post and relatively movable tuner members, a combined and integral tuning knob and drum mounted for rotary movement on one end portion of said mounting plate on an substantially parallel with said post and extending upwardly from said mounting plate, band guiding means extending upwardly from the other end portion of said mounting plate, an endless band of flexible material extending under tension around said guiding means and around and attached to said drum, and means connecting said movable tuner members respectively with opposite sides of said band.

2. Apparatus for supporting and operating permeability tuning radio mechanism of the movable core type, including in combination a narrow mounting plate, a post supported by and extending upwardly from the mid-portion of said mounting plate, a tuner comprising fixed members supported by said post and relatively movabl'e tuner members, a combined tuning knob and drum mounted for rotary movement on one end portion of said mounting plate and extending upwardly therefrom, band guiding means extending upwardly from the other end portion of said mounting plate, an endless band of flexible material extending under tension around said guiding means and around and attached to said drum, and means connecting said movable tuner mem-- bers respectively with opposite sides of said band, said post including a U-shaped member of sheet insulating material supporting said movable tuner members.

3. Apparatus for supporting and operating permeability tuning radio mechanism of the movable core type, including in combination a narrow mounting plate, a post of insulating material supported by and extending upwardly from the mid-portion of said mounting plate, a tuner comprising fixed members supported in laterally spaced relation by said post and relatively movable tuner members, a combined tuning knob and drum mounted for rotary movement on one end portion of said mounting plate and extend ing upwardly therefrom, band guiding means extending upwardly from the other end portion of said mounting plate, an endless band of flexible material extending under tension around said guiding means and around and attached to said drum, means connecting said movable tuner members respectively with opposite sides of said band, and a reinforcing tongue of metal extending from said mounting plate upwardly into said post between the fixed members of said tuner.

4. Apparatus for supporting and operating permeability tuning radio mechanism of the movable core type, including in combination a narrow mounting plate, a post supported by and extending upwardly from the mid-portion of said mounting plate, a tuner comprising fixed members supported by said post and relatively movable tuner members, a combined tuning knob and drum mounted for rotary movement on one end portion of said mounting plate and extending upwardly therefrom, band guiding means extending upwardly from the other end portion of said mounting plate, an endless band of flexible material extending under tension around said guiding means and around and attached to said drum, and means connecting said movable tuner members respectively with opposite sides of said band, said band guiding means including spaced rollers extending upwardly from said mounting plate and spring bearing studs extending upwardly from said mounting plate and through said rollers and subjecting said endless band to tensional stress.

5. Apparatus for supporting and operating permeability tuning radio mechanism of the movable core type, including in combination a narrow mounting plate, a post supported by and extending upwardly from the mid-portion of said mounting plate, a tuner comprising fixed members supported by said post and relatively movable tuner members,a combined tuning knob and drum mounted for rotary movement on one end portion of said mounting plate and extending upwardly therefrom, band guiding means extending upwardly from the other end portion of said mounting plate, an endless band of flexible material extending under tension around said guiding means and around and attached to said drum, and means connecting said movable tuner members respectively with opposite sides of said band, said band guiding means including spaced rollers extending upwardly from said. mounting plate and spring bearing studs extending upwardly from said mounting plate and through said rollers and subjecting said endless band to tensional stress, said spring studs comprising portions of the sides ofi a U-shaped member of spring wire having its mid-portion secured to said mounting plate.

6. Apparatus for supporting and operating permeability tuning radio mechanism of the movable core type, including in combination a narrow mounting plate, a post supported by and extending upwardly from the mid-portion of said mounting plate, tuner comprising fixed members supported by said post and relatively movable tuner members, a combined tuning knob and drum mounted for rotary movement on one end portion of said mounting plate and extending upwardly therefrom, band guiding means extending upwardly from the other end portion of said mounting plate, an endless band of flexible material extending under tension around said guiding means and around and attached to said drum, and means connecting said movable tuner members respectively with opposite sides of said band, said band guiding means including spaced rollers extending upwardly from said mounting plate and spring bearing studs extending upwardly from said mounting plate and through said roll ers and subjecting said endless band to tensional stress, said spring studs comprising portions of the sides of a U-shaped member of spring wire having its mid-portion secured to said mounting plate, said mounting plate having end notches containing said studs and an adjacent tongue engaging and holding the mid-portion of said U-shaped member, said U-shaped member extending from said holding tongue and below said mounting plate and upwardly through said end notches and continuing above said mounting plate to constitute said spring studs.

7. Apparatus for supporting and operating permeability tuning radio mechanism of the movable core type, including in combination, a narrow mounting plate, a post supported by and extending upwardly from the mid-portion of said mounting plate, a tuner comprising fixed members supported by said post and relatively movable tuner members, a combined tuning knob and drum mounted for rotary movement on one end portion of said mounting plate and extending upwardly therefrom, band guiding means extending upwardly from the other end portion of said mounting plate, an endless band of flexible material extending under tension around said guiding means and around and attached to said drum, means connecting said movable tuner members respectively with opposite sides of said band, said knob being hollow and of transparent material, a graduated scale in the hollow in said knob, and a pointer adjacent said scale and carried by said mounting plate.

WILLIAM A. SCI-IAPER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,217,984 Kirk Oct. 15, 1940 2,226,822 Kirk Dec. 31, 1940 2,260,599 Benton Oct. 28, 1941 2,270,117 Fill Jan. 13, 1942 2,272,433 Schaper Feb. 10, 1942 2,286,283 Kirk June 16, 1942 2,374,824 Leishman May 1, 1945 2,505,111 Hall Apr. 25, 1950 

